authors: tzung-her chen, kai-hsiang tsao, and kuo-chen wei source: proceedings of the 8th...
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Authors: Tzung-Her Chen, Kai-Hsiang Tsao, and Kuo-Chen Wei Source: Proceedings of The 8th International Conference on Intelligent System Design and Applications (ISDA 2008)
學生:張若怡 P78011044 許伯誠 P76011242
Date: 2013/01/18
Multiple-Image Encryption by Rotating Random Grids
Outline
Introduction Motivation Related Work Research Methods• Encryption phase • Decryption phase
Research Results Conclusion
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Introduction – Visual Cryptography
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Traditional Cryptography- Encryption and Decryption by computer
Visual Cryptography (VC), also called Visual Secret Sharing (VSS)- Encrypted by computer, Decrypted by human vision
Introduction
Traditional VC and Random Grid Traditional VC and Random Grid
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• VSS Traditional VC-based VSS (Codebook)RG-based VSS (Random Grid)
• Traditional VC-based VSS has at least two drawbacks as follows :1. Codebook design2. Pixel expansion
Introduction
Pixel expansionPixel expansion
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Secret image
Share1
Share2
Share1 + Share2
Traditional VC-based VSS:
Introduction
Traditional VC and Random Grid Traditional VC and Random Grid
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• VSS Traditional VC-based VSS (Codebook)RG-based VSS (Random Grid)
• Traditional VC-based VSS has at least two drawbacks as follows :1. Codebook design2. Pixel expansion
Motivation
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SA G1 G2 SA’
G1 G2
SA
SB
SA’
SB’
Related Work
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b g1 g2 g1⊕ g2
0 0 0 0 1 1 1
1 0 1 1 1 0 1
SA G1
for(i=0 ; i<w ; i++) for(j=0 ; j<h ; j++) if(B[i][j] == 0) G2[i][j] = G1[i][j]; else G2[i][j] = G1[i][j];Output(G1 , G2);
G2
Random Grid Algorithm1:
O. Kafri, and E. Keren, “Encryption of pictures and shapes by random grids,” Optics Letters, vol. 12, no. 6, 1987, pp. 377-379.
In 1987, Kafri and Keren propose three different algorithms to encrypt a binary secret image.
Research Methods
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Research Methods
Encryption phase:Step 1: SA(i, j) ← f RSP(SA).
Randomly select a pixel SA(i, j) from the first secret image SA, where the i-th row and the j-th column of the matrix SA are in the range of [0,m-1].
Step 2: G1(i, j)||G2(i, j) ← f RG(SA(i, j))
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Research Methods
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Research Methods
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Research Methods
Step 8: G1((m-1)-j, i) ← random(0,1)
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Research Methods
Decryption phase
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Research Results
Simulation 1: binary secrets, 90-degree rotation • Two secret images SA and SB with the size of 512×512
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Research Results
Simulation 2: Halftone secrets, 90-degree rotation • Two gray-level secret images SA and SB with the size of
512×512
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Research Results
Simulation 3: binary secrets, 180-degree rotation
Simulation 4: binary secrets, 270-degree rotation
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Conclusion
Property 1: No extra codebook redesigned Property 2: No extra pixel expansion introduced Property 3: Multiple secrets encoded Property 4: Bandwidth and storage saving Property 5: Wide image format
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